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Manuscript Title: Coulomb coefficients for complex ionic crystals.
Authors: D.C. Sutherland, W.G. Ferrier
Program title: KCOUL1
Catalogue identifier: ACWY_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 12(1976)179
Programming language: Algol.
Computer: ICL SYSTEM 4/75.
Operating system: EMAS.
RAM: 4K words
Word size: 32
Keywords: Solid state physics, Lattice dynamics, Coulomb coefficients, Complex ionic crystals, External modes.
Classification: 7.8.

Nature of problem:
The program evaluates Coulomb coefficients for complex ionic crystals using the equations given by Venkataraman and Sahni modified to take account of the work of Scheringer. These equations are a generalisation of the ones given by Kellermann.

Solution method:
The efficient evaluation of several convergent complex three-dimensional sums is central to the problem of obtaining the coefficients. The terms which control the convergence of the sums along the x, y, and z axes have been identified, together with limiting values for them. In the program preliminary calculations along the axes are made to find the indices at which the limiting values are reached. These indices are used as limits when calculating the sums in full.

Restrictions:
The symmetry of the crystal must be orthorhombic (P, F or I, but not C) or higher. There must only be two ions or ionic groups per primitive unit cell.